Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

No annotations are supplied, so the description carries the full load, and it does well: it discloses the paid cost ($0.01 USDC via x402 on eip155:8453), that execution is deterministic and read-only, that nothing is stored, and that private and local hosts are refused. It also previews the return shape (0-100 score, verdict enum, defects with fixes). It does not cover rate limits, timeouts, or failure behaviour, which keeps it below 5 for a network-touching, paid tool.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

A single dense paragraph that front-loads the payment tag, then the action, then the checklist, then the outputs, then the safety constraints. Nearly every clause carries information an agent needs. It is long but not padded; slightly heavier enumeration of checks could be trimmed without loss.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a two-parameter tool with no output schema, the description supplies the return contract (numeric score, one of three verdicts, defect list with fixes) and the operational constraints (paid, read-only, stateless, public hosts only), which is most of what an agent needs before calling. Remaining gaps are latency/expected duration and what to do with the defect output, i.e. hand off to doctor_repair_kit or doctor_upgrade_plan.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, so both 'url' and 'endpoint' are already documented in the schema, and the baseline is 3. The description adds one piece of meaning beyond the schema by framing 'endpoint' as the source of a live 402 challenge test and marking it optional, but adds nothing about URL normalization, path vs origin handling, or format expectations.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb and resource ('Diagnose another agent's discoverability') and enumerates exactly what gets inspected: robots.txt rules for AI crawlers, llms.txt, A2A agent card fields, MCP manifest, OpenAPI x402 metadata, and an optional live 402 challenge. That is far more specific than the name alone. It stops short of 5 because it never distinguishes itself from related siblings such as agent_ready_score, a2a_card_check, mcp_probe, or x402_probe, so an agent cannot tell from the description alone whether this supersedes or complements them.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

Usage is only implied: 'optionally a live 402 challenge on a given endpoint' hints that the endpoint parameter should be supplied when payment-readiness testing is wanted, and the overall framing implies 'use this to audit an agent/API origin'. There is no explicit statement of when to choose this over agent_ready_score or x402_probe, and no when-not guidance beyond the host restriction.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.